Cellulose-ether film and composition for making the same



Patented June, 10, 193i) STEWART J. CARROLL, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK OFFICE COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK OELLULOSE-ETHER'FILM AND COMPOSITION FOR MAKING THE SAME No Drawing.

:compositions the other properties of which are substantially colorless,

are also highly advantageous in the plastic and analogous arts, such, for instance, as the film or varnish arts.

One object of the invention is to provide cellulose ether films having not only all of the ordinary desirable qualities of films for photographic purposes, but also having unusually low inflammability and extremely high resistance to deterioration by heat. Another object of the invention is to provide permanently transparent, strong, flexible sheets or films of desired thinness, which are substantially waterproof, are unaffected by ordinary photographic fluids,

are substantially without harmful action upon lightsensitive photographic coatings, are of low inflammability and highly resistant to prolonged heating. Another object of the 'invention is to provide compositions capable of easy manipulation in film making, varnish making, or allied plastic arts. Another object is to provide compositions which will not injure or be injured by the substances or surfaces with which they are associated during manufacture, storage or use. Other objects will hereinafter appear.

In U. S. Patent No. 1,188,376 Lilienfeld, June 20th, 1916, there are disclosed a series of alkyl ethers of cellulose. Certain of these are particularly insoluble in water, and the present invention finds its chief value in connection with ethers having this property, such as water-insoluble ethyl cellulose, films of which have small shrinkage characteristics, aftertreatment in photographic baths. In U. S. Patent No. 1,583,709, Webb, May 4th,

' 1926, there are disclosed films of such cellulose ethers in which the ordinary desirable qualities-of photographic film base are combined with resistance to prolonged heating, this result being brought about by maintaining an alkalinity in excess of pH 7. It is desirable that such films, especially motion pic- Application filed August 9, 1926. Serial No. 128,338.

ture films, be capablepf withstanding heating without becoming brittle. 4 Whether or not films will possess this property can be foretold with practical accuracy by testing samples, say by heating them for weeks and even months at'a continuous temperature of 65 C. Films which remain usefully flexible after such a severe test are capable of withstanding the conditions met with in use. b

I have found that these qualities of the films may be maintained and yet the inflammability greatly lowered by incorporating in such films and in the compositions out of Which they are made, one or more of the bromnucleo (mono and polybrom) substitution products of naphthalene, anthracene and their homologues. The isomers resulting from different positions of the brom atoms on the rings, are all usable. On account of its-relative cheapness and simplicity of manufacture, I prefer alpha bromnaphthalene. All ofthese-substances, when mixed into the film-making compositions, should be free from free bromine and free hydrobromic acid. Otherwise they will cause sufiicient discoloration to make the film undesirable for photographic purposes, will cause deterioration of any photographic emulsions placed upon the films, and will destroy the alkalinity upon which the resistance of the .film to prolonged heating depends.

But I have found, as stated above, that if the brominated products are initially purified from free bromine and free hydrobromic acid and are incorporated in films having an alkalinity greater than pH'7, there is no acidity in the film-making solution, nor in the film, nor does this-condition develop during I the normal storage of the solution or during the normal useful life of the film.

I shall now give one example of my invention by way of illustration, but it will be bromnaphthalene in 300 to 500 parts of a volatile common solvent. The latter may- 'usefully comprise a mixture of methyl acetate and methyl alcohol, the 'weight of the methyl acetate being approximately nine times the weight of the methyl alcohol. Of course,'the ingredients of the solvent are of sufiicient purity to avoid acidifying the comthe brominated bodies mentioned hereinabove, or mixtures of them. By reason of the fact that these brominated products are of the nucleo type, having the bromine atoms directly bonded to the ring of carbon atoms, they are particularly stable.

The ingredients in the film-forming composition are thoroughly mixedand may be filtered if desired. l/Vhen more flowable solutions are desired, or when the compositions are tov be employed as lacquers, the volatile solvent may be increased until the desired viscosity is obtained, or volatile liquids, such as benzol, alcohol, and the like may be added to the thinner. Along with the ingredients mentioned above, I may add one or more supplementaryorganic bodies of only slight volatility which enhance the flexibility of the compositions and regulate the preparation of film therefrom; but such bodies are not essential. Examples of them are amyl or butyl acetate, the various amyl alcohols the various butyl alcohols, and mixtures oi them. Of course, these ingredients are also suificiently pure to be non-acid.

Films prepared from the hereinabove described compositions are flexible, smooth,

transparent, strong, substantially colorless, substantially waterproof, are unaffected by ordinaryphotographic baths, and in addition, combine unexpectedly low inflammability with high resistance against brittleness upon prolonged heating at 65 C., or equivalent conditions in actual use. The amount of alkali in the films is, of course, insufiicient to impaintheir transparency.

Having thus described my invention, what I claim as new and desire to secure by Letters'Patent is:

1. A fiowable film-forming composition comprising a water-insoluble cellulose ether, a brom-nucleo substitution product of the class comprising naphthalene, anthracene, and their homologues, which product is substantially free from uncombined bromine and hydrobromic acid, and a solvent common to said ingredients, said composition being. stabilized by the presence therein of inorganic alkali which creates an alkalinity in the composition in excess of pH 7 the specified ingredients being present in such proportions as to produce a transparent, colorless flexible film.

A flowable film-forming composition comprising 100 parts by weight of waterinsoluble cthyl cellulose, 5 to 50 parts of alpha bromnaphthalene substantially free from uncombined bromine and hydrobromic\ acid, and more than 300 parts of a volatile common solvent, said composition comprising sufiicient inorganic alkali to give it an alkalinity in excess of p117 the specified ingedients being present in suchproportions afiilto produce a transparent, colorless, flexible 3. As an article of manufacture a flexible, transparent, colorless film comprising (:01- loidiaed water-insoluble cellulose ether and a brom-nucleo substitution product of the class comprising naphthalene, anthracene, and their homologues, said product being substantially free from uncombined bromine and hydrobromic acid, said film having dis-' 

